This invention generally relates to infrared (xe2x80x9cIRxe2x80x9d) enabled touch systems or touch screens. More particularly, the present invention is directed to an inventive system and method to improve the resolution of IR touch systems. The system and method provide a higher resolution for determining the location of a touch on the screen through the use of on-axis and off-axis IR transmitter-receiver detection. In one embodiment of the inventive method, the touch location is determined by a multiple-step process of first identifying a coarse touch location and then determining a finer location for the touch within the coarse location area. The increased resolution of touch location is achievable with the inventive system and method without the need for an increased density of IR transmitters and receivers or the need for increased processor speed.
Touch systems are becoming more prevalent in everyday activities. In addition to touch systems being used in money access centers, lobby directories, museum and entertainment kiosks, and automobile positioning system displays, miniaturized touch systems have become the technology medium of choice for pocket diaries and organizers. While IR touch systems may be used in these applications, in order to be successful in these and other emerging markets, the determination of touch location in touch systems, including IR touch systems, must be made quickly, accurately and precisely. This is especially the case for pocket diaries which may use a relatively small point stylus or pointer as the user""s means of identifying a desired operation or system selection.
Generally, the location of a touch is identified through use of IR transmitters, typically light emitting diodes (xe2x80x9cLEDsxe2x80x9d), and IR receivers, typically phototransistors (xe2x80x9cphotosxe2x80x9d). An example illustration of a prior art touch screen is shown in FIG. 1. A set of n IR transmitters 20(1) to 20(n) and another set of m IR transmitters 40(1) to 40(m), for example LEDs, are positioned along two adjacent edges of a touch screen 11. A set of n IR receivers 30(1) to 30(n) and another set of m IR receivers 50(1) to 50(m), are positioned along the opposite edges of the touch screen 11 such that each receiver 30(i) and 50(i) is aligned on-axis with an opposing transmitter, respectively 20(i) and 40(i). As defined, transmitters 20(i) and 40(i) and receivers 30(i) and 50(i) mean each sequential transmitter and receiver where i=1, 2, 3, i, i+1, . . . , nxe2x88x921, n, for the n transmitters and respective receivers, and where i=1, 2, 3, i, i+1, . . . , mxe2x88x921, m, for the m transmitters and respective receivers.
In the conventional prior art touch system, the number of transmitters used along the screen perimeter equals the number of receivers positioned along the opposing screen edge, because the transmitters are each aligned on-axis with a receiver. As shown in FIG. 1, the typical touch screen 11 creates a Cartesian coordinate grid of x-coordinate transmitter-receiver pairs, for example x-coordinate pair 20(1) and 30(1), and y-coordinate transmitter-receiver pairs, for example y-coordinate pair 40(3) and 50(3). The detection pattern is accordingly an orthogonal grid of x and y coordinates.
The location of a touch is determined by scanning the x-coordinate pairs and y-coordinate pairs and identifying which transmitter-receiver pairs show a blockage of IR light. The scanning process entails activation of each receiver 30(i) and 50(i) and activating, or flashing, the opposing transmitter respectively 20(i) and 40(i), detecting whether the transmitter 20(i) and 40(i) IR signal is received by the respective on-axis receiver 30(i) or 50(i), and then deactivating each receiver 30(i) and 50(i). This receiver activation, on-axis transmitter flash, receiver deactivation process is repeated for each on-axis transmitter-receiver pair until all transmitter-receiver pairs are scanned.
The accuracy and precision of the location of a touch for a conventional touch system is dependent upon the density or number of transmitters and receivers positioned along the perimeter of the screen 11. One problem with such an orthogonal detection pattern, as illustrated in FIG. 1, is that if a touch diameter 95 is less than the spacing of adjacent transmitters and adjacent receivers, a touch may go undetected as being in an area where no beam crosses.
Moreover, the time period required to make the touch location determination is dependent upon the speed of the processor used to activate and flash the transmitters and receivers, and to detect whether the emitted IR signal is received by the receiver. Obviously, unless the processing capability of the system is increased, as more transmitter-receiver pairs are included in the touch system, the time to identify a touch location will increase along with the time period to scan the complete set of transmitter-receiver pairs.
Because the IR transmitters and receivers, or system optoelectronics, comprise a significant portion of the overall cost of an IR touch system, an increase in the number of optoelectronic devices would result in a dramatic increase in the overall system cost. Similarly, because the processor electronics are another significant portion of the cost of an IR touch system, an increase in processing speed to maintain a maximum time period for touch identification, would likewise cause a substantial increase in the system cost.
In addition to the noted on-axis conventional touch systems, one device described in Japanese Patent Application No. TOKKAI HEI 11-232024 for an Optical Position Detection Device, owned by Alpine Electronics, Inc., provides for the detection of two or more adjacent phototransistors within the range of light emitted from an opposing light emitting diode. The object of the Alpine system is to eliminate the restrictions of the prior art with respect to the number, position and placement of LEDs and phototransistors that would allow for possible improvements in position detection accuracy. While apparently describing detection of LED output through the use of off-axis phototransistors, the Alpine system does not appear to describe or disclose any method for efficiently scanning the LED-phototransistor pairs. Indeed, the device operation description appears to call for the sequential cycling all LEDs and detecting multiple phototransistors for each of the LEDs activated. Such a device would require significantly increased computer processing capability to handle the increased information provided from detecting multiple phototransistors for every LED, and cycling through each LED along the perimeter of the touch screen.
Accordingly, there is a need for a IR touch system that has an improved resolution capability for accurately and precisely identifying the location of a touch, but that does not require significantly more IR transmitters and receivers, and does not require significantly increased computer processing requirements to control the transmitter and receivers and process the data resulting from the scanning operation. Such a system or method does not currently exist, but would greatly extend the utility and capability of IR touch screen systems.
In view of the shortcomings of the prior art, it is an object of the present invention to provide an improved resolution infrared touch system and method that provides an accurate and precise determination of the location of a touch without increasing the number of touch screen IR transmitters or IR receivers. It is a further object of the present invention that the improved touch position resolution does not necessitate extended or higher speed processing requirements to maintain system resolution and speed of operation.
To achieve this and other objects, and in view of its purposes, the present invention provides an infrared touch system having increased resolution for determining position of a touch on a touch screen, the infrared touch system comprising a first plurality of infrared transmitters positioned along a first edge of the touch screen, each infrared transmitter of the first plurality of infrared transmitters controllably emitting a cone of infrared light; a first plurality of infrared receivers positioned along a second edge of the touch screen directly opposite from the first plurality of transmitters, whereby each receiver of the first plurality of infrared receivers is aligned on-axis with one infrared transmitter of the first plurality of transmitters and is off-axis to each of the other first plurality of transmitters; a second plurality of infrared transmitters positioned along a third edge of the touch screen, the third edge being approximately perpendicular to the first and second edge of the touch screen, each infrared transmitter of the second plurality of infrared transmitters controllably emitting a cone of infrared light; a second plurality of infrared receivers positioned along a fourth edge of the touch screen opposite from the second plurality of transmitters, whereby each receiver of the second plurality of infrared receivers is aligned on-axis with one infrared transmitter of the second plurality of transmitters and is off-axis to each of the other second plurality of transmitters; a processor to control activation of the first and second plurality of infrared transmitters and control activation of the first and second plurality of infrared receivers and for calculating the touch position on the touch screen using on-axis and off-axis activation of the infrared transmitters and receivers.
It is a further object of the present invention to provide an infrared touch system having a touch screen, said infrared touch system comprising a first plurality of infrared transmitters positioned along a first edge of a touch screen, each infrared transmitter of the first plurality of infrared transmitters controllably emitting infrared light; a first plurality of infrared receivers positioned along a second edge of the touch screen opposite from the first plurality of transmitters, whereby each receiver of the first plurality of infrared receivers is aligned on-axis with one infrared transmitter of the first plurality of transmitters and is off-axis to each of the other first plurality of transmitters, further whereby an infrared beam of light emitted from each transmitter of the first plurality of infrared transmitters is receivable by at least two infrared receivers of the first plurality of infrared receivers; a second plurality of infrared transmitters positioned along a third edge of the touch screen, each infrared transmitter of the second plurality of infrared transmitters controllably emitting infrared light; a second plurality of infrared receivers positioned along a fourth edge of the touch screen opposite from the second plurality of transmitters, whereby each receiver of the second plurality of infrared receivers is aligned on-axis with one infrared transmitter of the second plurality of transmitters and is off-axis to each of the other second plurality of transmitters, further whereby an infrared beam of light emitted from each transmitter of the second plurality of infrared transmitters is receivable by at least two infrared receivers of the second plurality of infrared receivers; a first processor to sequentially activate each of the first and second plurality of infrared transmitters and opposing first and second plurality of infrared receivers; and a second processor for calculating a touch position on the touch screen, wherein the second processor identifies a coarse x-coordinate touch area based upon identification of blocked infrared beams between activated transmitters and receivers; identifies a coarse y-coordinate touch area based upon identification of blocked infrared beams between activated transmitters and receivers; calculates a coarse x-coordinate and y-coordinate touch area from the identified coarse x-coordinate and y-coordinate touch areas; and refines the x-coordinate and y-coordinate touch location based upon systematic activation of off-axis transmitter and receiver pairs having infrared beams that cross the calculated coarse touch area.
It is a further object of the present invention to provide a method of determining a touch location on a touch system screen, the screen having along first and second adjacent edges a plurality of infrared transmitters and the touch screen further having a plurality of infrared receivers along third and fourth adjacent edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of estimating a coarse touch location based upon a systematic on-axis activation of each infrared transmitter and opposing receiver; and refining the touch location based upon a systematic off-axis activation of selected infrared transmitters and receivers.
It is a further object of the present invention to provide a method of determining a touch location on a touch system screen, the touch screen having along first and second adjacent edges a plurality of infrared transmitters and the touch screen further having a plurality of infrared receivers along third and fourth adjacent edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of estimating a coarse touch location based upon a systematic on-axis activation of each infrared transmitter and opposing receiver; selecting off-axis transmitter and receiver pairs based upon the coarse touch location estimate; and refining the touch location based upon a systematic activation of the selected off-axis transmitter and receiver pairs.
It is still a further object of the present invention to provide a method of determining a touch location on a touch system screen, the touch screen having along an x-coordinate edge, a first plurality of infrared x-coordinate transmitters and along a y-coordinate edge, a second plurality of y-coordinate infrared transmitters, the touch screen further having a plurality of infrared receivers along two edges opposing the plurality of infrared transmitters, such that each transmitter is aligned on-axis to one receiver, the method comprising the steps of estimating a coarse x-coordinate and y-coordinate touch location on the touch screen based upon systematic on-axis activation of each infrared transmitter and opposing receiver; selecting off-axis transmitter and receiver x-coordinate pairs based upon the coarse y-coordinate touch location estimate; refining the x-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver x-coordinate pairs; selecting off-axis transmitter and receiver y-coordinate pairs based upon the coarse x-coordinate touch location estimate; and refining the y-coordinate touch location based upon systematic activation of the selected off-axis transmitter and receiver y-coordinate pairs.
These and other aspects of the present invention are set forth below with reference to the drawings and the detailed description of certain preferred embodiments. It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are not intended to be or should be considered restrictive of the invention.